The prior art has provided a number of procedures for preparing dry beverage tablets. In U.S. Pat. No. 2,889,226 to Hinkley and U.S. Pat. No. 3,660,107 to Mayer, effervescent couples are added to tabletted dry beverage mixes to improve the rate of solubility of the highly compressed tablets. Hinkley employs a wetting agent in addition to the effervescent materials.
While not directly related to the preparation of beverage tables, U.S. Pat. Nos. 3,653,914 and 4,004,036 to Schmitt describe the preparation of rapidly-soluble sweetener tablets for use in hot or aqueous media. In preparing the tablets, a minor amount of water is added with an organic solvent to release a portion of the CO.sub.2 from an effervescent couple which is employed to aid in dissolving the tablet. The release of CO.sub.2 during molding is said to achieve a porous structure. U.S. Pat. No. 4,004,036 indicates that the tablet is weaker than would be desired but can be strengthened by contacting the formed tablet with an organic solvent.
In U.S. Pat. No. 2,851,361 to Diller, there is disclosed a tablet for preparing a carbonated soft drink in cold water. It is indicated that the density of the tablet is a critical factor and should be about 1.3 grams per cubic centimeter. The patent discloses that because it is difficult to secure the desired high density, the tablet can be compressed while removing entrapped air. The patent further suggests that a lubricated die using a pressure of about 4,000 pounds per square inch, psig (281.2 kilograms per square centimeter, Kg/Cm.sup.2) is appropriate.
U.S. Pat. No. 3,667,962 to Fritzberg et al., indicates that the solubility of tablets for preparing carbonated beverages can be improved by forming separate acid and carbonate portions which are both highly porous and friable. In the paragraph bridging columns 3 and 4 of this patent, it is indicated that these puffed materials can be crushed to powdered form. Thus, while Fritzberg et al. disclose a way to improve solubility, they do so without concern for structural strength of the formed product.
In U.S. Pat. No. 4,031,238 to Reid et al., there is disclosed a water-soluble, solid beverage cube consisting of powdered glucose monohydrate, sucrose and a hygroscopic flavor material. According to the disclosure, this mixture is heated in a closed or moistened environment and then shaped to final form. This is said to be an improvement upon the disclosed prior art procedure of combining a flavor material with a vehicle such as ethyl alcohol and water to form a damp, non-cohesive powder which is then formed into a cube under pressure and dried to evaporate the vehicle.
In U.S. Pat. No. 4,508,740 to McSweeney, an aspartame-sweetened beverage tablet is formulated with a moistener consisting of water, propylene glycol or ethyl alcohol, monocalcium phosphate and glycerine or a glycerine derivative.
Hence, there remains a present need for a sugar-free sweetened, unitary dry beverage composition in the form of a soluble, yet structurally-strong tablet, and a process for preparing such a product.